Material having characteristics of high thermal conductivity and electromagnetic interference resistance

ABSTRACT

A compound material at least comprises a pair of overlapped high heat conductive layer and electromagnetic interference (EMI) shielding layer. The EMI shielding layer includes a high heat conductive sub-layer and a plurality of EMI shielding blocks thereby forming an EMI shielding net and a heat conducting track with the cooperation of the overlapped heat conductive layer in the meantime. The compound material further comprises a second EMI shielding layer overlapped on the side of the heat conductive layer which is opposite to said EMI shielding layer and having a plurality of EMI shielding blocks, which are arranged in a similar as and are staggered from the EMI shielding blocks of said EMI shielding layer in the overlapped or vertical direction thereof.

TECHNICAL FIELD

[0001] The present invention relates to a compound material, especiallyto a compound material having both the characteristics of super thermalconductivity and electromagnetic interference resistance in themeantime.

DESCRIPTION OF RELATED ARTS

[0002] Electronic or electrical devices, especially those running withhigh power, are inevitably confronted with the problem of thermaldissipation. The traditional method to solve this problem is toadditionally equip themselves with a special means or device todissipate heat occurred therefrom, for example, a forcible convectionsystem consisted of one or more fan fins.

[0003] However, as far as those small or micro electronic elements suchas a CPU, which are used in compression circumstances, for example, aremounted on printed circuit boards, it's far from enough to use saidforcible convection system to solve the heat dissipation problem becauseno enough heat dissipation area can be available. Hence, at least aradiator like device with more fan fins and high thermal conductivitythereof should be added onto the heat dissipating surface of the CPU.

[0004] Commonly, said radiator like devices having several fan fins aremade of a kind of metal material such as aluminum alloys which is rigid.But, when said devices are mounted onto the CPU, a small space willunavoidably be left therebetween which will allow air to be filledtherebetween. Since air is not a good heat conductor, the performance ofthe whole heat dissipation system will be adversely affected.

[0005] Hence, a new soft material with high thermal conductivity thereofis expected to be adopted between the CPU and the radiator like deviceso that no air space will be remained therebetween.

[0006] Furthermore, when the electronic elements work, special measuresstill have to be adopted to overcome the electromagnetic interference(EMI) problem which is brought to other surrounding electronic elementsbecause of the running with high speed or under high power, otherwisethe other electronic elements may not be able to work normally.

[0007] Therefore, devices, which can conduct heat well and help toresist EMI thereof, are on demand. Relevant prior arts can refer to aChinese patent ZL91101947.2 issued on Mar. 15, 2000. This patentdiscloses an EMI shielding device used on printed circuit board (PCB),which is essentially a shell made of thermal conducting materials.However, the shell can only perform its anti EMI and heat dissipationfunctions when it is connected to a grounding means set on the PCB. As aresult, corresponding additional circuitries shall be pre-set on thePCB, which not only complicate the according circuit design, but alsooccupy the very limited space of the PCB.

[0008] So, people then turn to pursue other possible resolutions such astrying to find a special material which has both the characteristics ofhigh thermal conductivity and EMI resistance. Taiwan patent TW345667gives a compound magnetic material with high thermal conductivity. Thismaterial is produced by dispersing some soft magnetic powder and somethermal conductive powder into an organic bonding material. As the totalamount of the soft magnetic powder and thermal conductive powder whichis allowed in the organic bonding material is limited, the accordingperformance of both heat conduct and EMI resistance is not as good asexpected.

[0009] Another prior art is to adopt a resin as the base material anddisperse Al₂O₃ powder and silicone powder into the resin base. Althoughthe resulted material is soft and has good heat conductivity, it can notbe used to shield EMI.

[0010] In addition, there is a kind of electromagnetic wave absorbingmaterial which is formed by adding some soft magnetic powder into aplastic base material. Since this wave absorbing material only canperform a good EMI shielding function while is a poor heat conductivematerial, the conventional application of this material for a CPU usageis to firstly form a hollow body in rectangular or columned shape and toattach the hollow body onto the CPU together with a few heat dissipatingfins positioned in the hollow part of the hollow body. In order to gainbetter performance, additional heat dissipating fins or a small fan canalso be attached onto the fins in the hollow body. Such measures canincrease heat conducting effects thereof, however, it will decrease theelectromagnetic wave absorbing effects thereof.

SUMMARY OF THE INVENTION

[0011] A main object of the present invention is to provide a compoundmaterial having both the characteristics of high thermal conductivityand EMI resistance.

[0012] In order to achieve the objects set forth, a compound materialwith both the characteristics of high thermal conductivity and EMIresistance comprises a first high heat conductive layer and a first EMIshielding layer.

[0013] The compound material in accordance with the present inventionfurther comprises a few alternately superposed high heat conductivelayers and EMI shielding layers. The amount of the high heat conductivelayers and EMI shielding layers can be determined according to actualrequirements and the thickness of each layer can also be determined byaccording actual needs thereof.

[0014] The first high heat conductive layer and the first EMI shieldinglayer is superposed together. The first EMI shielding layer istessellated and comprises a high heat conductive sub-layer. The EMIshielding material is filled separately and alternately in the sub-layerthereby forming a plurality of EMI shielding blocks of the first EMIshielding layer. The EMI shielding material is a kind of material whichcan absorb electromagnetic waves, and can be integrated with thesub-layer by planography printing or insert-molding methods.

[0015] The compound material in accordance with the present inventionfurther has a second high heat conductive layer. The second heatconductive layer is superposed on one side of the first EMI shieldinglayer opposite to the first high heat conductive layer. A second EMIshielding layer is superposed on one side of the second high heatconductive layer opposite to the first EMI shielding layer. Thestructure of the second EMI shielding layer is similar to the first EMIshielding layer, but the positions of the EMI shielding blocks in thesecond EMI shielding layer are staggered relative to the positions ofthe EMI shielding blocks in the first EMI shielding layer in theoverlapping or vertical direction thereof.

[0016] The present invention adopts a design of alternately overlappedhigh heat conductive layers and EMI shielding layers. Each EMI shieldinglayer has a high heat conductive sub-layer in which according EMIshielding material is filled separately and alternately thereby forminga plurality of EMI shielding blocks, which makes each EMI shieldinglayer look tessellated and form a plurality of pre-set compartedportions (i.e., the EMI shielding blocks).

[0017] Furthermore, the positions of the EMI shielding blocks indifferent EMI shielding layers are staggered relative to the positionsof the EMI shielding blocks in the first EMI shielding layer in theoverlapping or vertical direction. Therefore, the accordingly staggeredheat conductive portions of the high heat conductive sub-layers of theEMI shielding layers and the overlapped heat conductive layers can forma heat conducting track which is staggered, consecutive and sinuous,which can guarantee the high thermal conductivity of the compoundmaterial in accordance with the present invention.

[0018] In the meantime, since each EMI shielding layer has tessellatedlydistributed EMI shielding material blocks and the EMI shielding blocksof different EMI shielding layers are staggered from each other in theoverlapping direction thereof, a complete electromagnetic wavesabsorbing net is thus formed, which can ensure the super EMI shieldingperformance of the compound material in accordance with the presentinvention.

[0019] In addition, the compound material in accordance with the presentinvention can be made into various shapes as desired, and thenpositioned onto correspondent electronic elements or devices. Hence, noadditional circuitry design is needed with the application of thepresent invention which results in advantages of easy use andreliability, etc.

[0020] Other objects, advantages and novel features of the inventionwill become more apparent from the following detailed description whentaken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021]FIG. 1 is a sectional sketch view of the compound material inaccordance with the present invention; and

[0022]FIG. 2 is a plan sketch view of an EMI shielding layer of thecompound material in accordance with the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

[0023] Referring to FIGS. 1 and 2, a compound material having thecharacteristics of high thermal conductivity and electromagneticinterference (EMI) resistance of the present invention is shown.

[0024]FIG. 1 shows a sectional sketch view of the compound material. Thecompound material comprises a first high heat conductive layer 1, afirst EMI shielding layer 2, a second high heat conductive layer 3, asecond EMI shielding layer 4 and a third high heat conductive layer 5.

[0025] The amounts of the heat conductive layers (1, 3, 5) and the EMIshielding layers (2, 4) can be adjusted according to actualrequirements. The thickness of each heat conductive layer (1, 3, 5) oreach EMI shielding layer (2, 4) can be pre-set according to actualapplication environments.

[0026] The second heat conductive layer 3 is superposed over one side ofthe first EMI shielding layer 2, which is opposite to the first heatconductive layer 1. The second EMI shielding layer 4 is overlapped overone side of the second heat conductive layer 3 in a way just like theway the second heat conductive layer 3 overlapped onto the first EMIshielding layer 2, and the position of the second EMI shielding layer 4is opposite to the first EMI shielding layer 2.

[0027] The structures of the first and second EMI shielding layers 2 and4 are both tessellated and each includes a high heat conductivesub-layer 23 or 43. EMI shielding material is separately and alternatelyfilled into the heat conducting sub-layer 23 so as to form correspondingEMI shielding blocks 22, 42 which are alternately separated so that thearrangement of each EMI shielding layer 2, 4, or other added ones asrequired, looks like a chess board or is a tessellation.

[0028] The structure of the second EMI shielding layer 4 is similar tothe first EMI shielding layer 2, but the positions of the EMI shieldingblocks 42 of the second EMI shielding layer 4 are staggered relative tothe positions of the EMI shielding blocks 22 in the first EMI shieldinglayer 2 in the overlapping or vertical direction thereof.

[0029] The EMI shielding material forming the EMI shielding blocks 22and 42 of the first and second EMI shielding layers 2 and 4 is a kind ofelectromagnetic waves absorbing material. The arrangements of EMIshielding blocks 22 and 42 of the first and second EMI shielding layers2 and 4 are tessellated in the according heat conducting sub-layers 23and 7 43. The EMI shielding material of the EMI shielding blocks 22 and42 can be integrated with the sub-layers 23 and 43 by planographyprinting or insert-molding methods.

[0030] The compound material in accordance with the present inventioncan further comprise more EMI shield layers and high heat conductivelayers which are alternately overlapped over each other and thestructures or compositions thereof are similar to the first and secondEMI shielding layers 2, 4 and the first and second heat conductivelayers 1, 3.

[0031] In the meantime, the EMI shielding blocks of each of the EMIshielding layers are all staggered from correspondent EMI shieldingblocks of the EMI shielding layer which is positioned adjacent to it inthe overlapping or vertical direction thereof, just like the way of thestaggered arrangement of the first and second EMI shielding layers 2 and4. Therefore, a complete electromagnetic waves absorbing net is thusformed which can ensure the super EMI shielding performance of thecompound material in accordance with the present invention.

[0032] Moreover, the accordingly staggered heat conductive portions ofthe high heat conductive sub-layers 23 and 43 of the first and secondEMI shielding layers 2, 4 and the overlapped heat conductive layers 1,3, 5 can form a heat conducting track which is staggered, consecutiveand sinuous, which can guarantee the high thermal conductivity of thecompound material in accordance with the present invention.

[0033] The process of making the compound material of the presentinvention is simply explained below.

[0034] Step 1: take a suitable high temperature thermoplastic materialwith good thermal resistance, such as SiC, as a base material, and theninfiltrate Al₂O₃ powder into the thermoplastic material base therebyforming a first high heat conductive layer 1;

[0035] Step 2: form a high heat conductive sub-layer 23 with tessellatedslots or holes therein over the first high heat conductive layer 1, theslots or holes are arranged separately and alternately;

[0036] Step 3: fill EMI shielding material into the slots or holes ofthe heat conductive sub-layer 23 thereby forming correspondent EMIshielding blocks 22 which are tessellated the same as those of the slotsor holes of the heat conductive sub-layer 23, and thus the first EMIshielding layer 2 is formed;

[0037] Step 4: overlapped on the first EMI shielding layer 2, the secondhigh heat conductive layer 3 is formed by infiltrating powder into ahigh temperature thermoplastic material base;

[0038] Step 5: form a high heat conductive sub-layer 43 with tessellatedslots or holes therein over the second high heat conducting layer 3, theslots or holes are arranged separately and alternately;

[0039] Step 6: fill EMI shielding material into the slots or holes ofthe heat conducting sub-layer 43 thereby forming correspondent EMIshielding blocks 42 which are tessellated the same as those of the slotsor holes of the heat conductive sub-layer 43, and thus the first EMIshielding layer 4 is formed, and the EMI shielding blocks 42 arestaggered from the EMI shielding blocks 22 of the first EMI shieldinglayer 2 in the overlapping or vertical direction thereof;

[0040] Step 7: overlapped on the second EMI shielding layer 4, the thirdhigh heat conducting layer 5 is formed by infiltrating Al₂O₃ powder intoa high temperature thermoplastic material base;

[0041] After repeat the similar steps as above-described, the compoundmaterial in accordance with the present invention can be made tocomprise a few alternately overlapped and integrated EMI shieldinglayers (2, 4) and high thermal conductive layers (1, 3, 5).

[0042] The present invention adopts a design of alternately overlappedhigh heat conductive layers (1, 3, 5) and EMI shielding layers (2, 4).Each EMI shielding layer has a high heat conductive sub-layer in whichaccording EMI shielding material is filled separately and alternately,which makes each EMI shielding layer look tessellated.

[0043] Furthermore, the positions of the EMI shielding blocks indifferent EMI shielding layers are staggered relative to the positionsof the EMI shielding blocks in the adjacent EMI shielding layers in theoverlapping or vertical direction. Therefore, the accordingly staggeredheat conductive portions of the high heat conductive sub-layers of theEMI shielding layers and the overlapped heat conductive layers can forma heat conducting track which is staggered, consecutive and sinuous,which can guarantee the high thermal conductivity of the compoundmaterial in accordance with the present invention.

[0044] In the meantime, since each EMI shielding layer has tessellatedlydistributed EMI shielding material blocks and the EMI shielding materialblocks of different EMI shielding layers are staggered from each otherin the overlapping direction thereof, a complete electromagnetic wavesabsorbing net is thus formed, which can ensure the super EMI shieldingperformance of the compound material in accordance with the presentinvention.

[0045] In addition, the compound material in accordance with the presentinvention can be made into various shapes as desired, and thenpositioned onto correspondent electronic elements or devices. Hence, noadditional circuitry design is needed with the application of thepresent invention which results in advantages of easy use andreliability, etc.

[0046] It is to be understood, however, that even though numerouscharacteristics and advantages of the present invention have been setforth in the foregoing description, together with details of thestructure and function of the invention, the disclosure is illustrativeonly, and changes may be made in detail, especially in matters of shape,size, and arrangement of parts within the principles of the invention tothe full extent indicated by the broad general meaning of the terms inwhich the appended claims are expressed.

1. A compound material at least comprises a first high heat conductivelayer and a first electromagnetic interference (EMI) shielding layerwhich are integrated together, among which the first EMI shielding layerforms a plurality of pre-set comparted portions.
 2. The compoundmaterial as claimed in claim 1, wherein the first high heat conductivelayer and the first EMI shielding layer are overlapped in a verticaldirection thereof.
 3. The compound material as claimed in claim 2,wherein the arrangement of the comparted portions of the first EMIshielding layer is tessellated.
 4. The compound material as claimed inclaim 3, wherein the comparted portions are a plurality of EMI shieldingblocks formed by filling EMI shielding material into correspondent slotsin a high heat conductive sub-layer of the first EMI shielding layer. 5.The compound material as claimed in claim 4, wherein the EMI shieldingblocks are separately and alternately arranged in the heat conductivesub-layer of the first EMI shielding layer.
 6. The compound material asclaimed in claim 5, wherein the EMI shielding blocks are made from anelectromagnetic wave absorbing material
 7. The compound material asclaimed in claim 6, wherein the EMI shielding blocks are integrated withthe heat conductive sub-layer by planography printing or insert-moldingmethods.
 8. The compound material as claimed in claim 7, wherein thecompound material further comprises a second high heat conductive layerwhich is overlapped on the first EMI shielding layer and opposite to thefirst heat conductive layer.
 9. The compound material as claimed inclaim 8, wherein the compound material further comprises a second EMIshielding layer which is overlapped on the second heat conductive layerand opposite to the first EMI shielding layer.
 10. The compound materialas claimed in claim 9, wherein the second EMI shielding layer alsoincludes a plurality of EMI shielding blocks, which are formed in asimilar way as those of the first EMI shielding layer and are staggeredfrom the corresponding EMI shielding blocks of the first EMI shieldinglayer in the overlapped or vertical direction thereof.
 11. The compoundmaterial as claimed in claim 10, wherein the compound material furthercomprises a third high heat conductive layer which is overlapped on thesecond EMI shielding layer and opposite to the second heat conductivelayer.
 12. A compound material at least comprises a pair of overlappedhigh heat conductive layer and electromagnetic interference (EMI)shielding layer, the EMI shielding layer including a high heatconductive sub-layer and a plurality of EMI shielding blocks therebyforming an EMI shielding net and a heat conducting track with thecooperation of the overlapped heat conductive layer in the meantime. 13.The compound material as claimed in claim 12, wherein the heatconductive sub-layer has a plurality of slots therein and a suitable EMIshielding material is filled into the slots thereby forming the EMIshielding blocks thereof.
 14. The compound material as claimed in claim13, wherein the EMI shielding blocks are alternately and separatelyarranged in the heat conductive sub-layer.
 15. The compound material asclaimed in claim 14, wherein the EMI shielding blocks are integratedwith the heat conductive sub-layer by planography printing orinsert-molding methods.
 16. The compound material as claimed in claim15, wherein further comprises a second EMI shielding layer overlapped onthe side of the heat conductive layer which is opposite to said EMIshielding layer.
 17. The compound material as claimed in claim 16,wherein the second EMI shielding layer also has a high heat conductivesub-layer forming a plurality of slots therein and a plurality of EMIshielding blocks which is formed by filling EMI shielding material intothe slots of the heat conductive sub-layer.
 18. The compound material asclaimed in claim 17, wherein the EMI shielding blocks of the second EMIshielding layer are arranged in a similar as the EMI shielding blocks ofsaid EMI shielding layer.
 19. The compound material as claimed in claim18, wherein the EMI shielding blocks of the second EMI shielding layerare staggered from the EMI shielding blocks of said EMI shielding layerin the overlapped or vertical direction thereof.
 20. The compoundmaterial as claimed in claim 12, wherein the material of the EMIshielding blocks of said EMI shielding layer and the second EMIshielding layer is a suitable electromagnetic wave absorbing material.21. The compound material as claimed in claim 20, wherein the heatconductive layer and the heat conductive sub-layer are formed byinfiltrating Al₂O₃ powder into a suitable thermoplastic base material.22. The compound material as claimed in claim 13, wherein the materialof the EMI shielding blocks of said EMI shielding layer and the secondEMI shielding layer is a suitable electromagnetic wave absorbingmaterial.
 23. The compound material as claimed in claim 16, wherein thematerial of the EMI shielding blocks of said EMI shielding layer and thesecond EMI shielding layer is a suitable electromagnetic wave absorbingmaterial.
 24. The compound material as claimed in claim 19, wherein thematerial of the EMI shielding blocks of said EMI shielding layer and thesecond EMI shielding layer is a suitable electromagnetic wave absorbingmaterial.